The objective is to understand the role of the mechanical (elastic-fluid) activity of the cochlea in the transformation of sound into receptor cell stimulation. Recent calculations for straight box models of the guinea pig cochlea have produced good correlation between the in vivo and post mortem experiments of other investigators on basilar membrane stiffness and response, as well as spiral ganglion cell recordings from cochleas devoid of outer hair cells due to kanamycin treatment. It appears that the normal peak neural excitation occurs some 1 mm apical of the peak basilar membrane amplitude, which focuses attention on the micromechanics of the sensory epithelium. Work on a cochlear model simulating the organ of Corti has progressed. The calculations indicate substantially higher pressure in the inner sulcus and the presence of two traveling waves. A specific objective of the proposed effort will be to clarify the behavior with and without attachment of the "tectorial membrane". Now that accurate calculations for realistic physical models are possible, the necessity for accurate quantitative measurement of the elastic properties of the cochlear tissue is more evident. A transducer for measuring forces down to 1 dyne is being constructed and will be used during this year of effort on post mortem preparations of human and cat cochleas.